Current studies will continue. These are: 1) Examination for rabbit sperm antigens essential in reproduction. Fab antisperm antibody fragments of heterologous origin are used to recognize immunologically vulnerable steps in reprodction by inhibitory action in in vivo and in vitro artificial insemination experiments. The function, biochemistry and cytochemistry of any inhibiting antigens are then explored. Additionally, recognized sperm macromolecules (e.g. membrane proteins, acrosomal enzymes) are investigated. "Essential" antigens are then examined for iso- and autoantigenicity and, in positive cases, purified and tested for antifertility vaccine potential. Sperm hyaluronidase, an isoantigen in female rabbits, is currently being so tested. 2) Immunological infertility could result from secondary antibody action not involving blockade of essential "fertilization antigens"; for example complement dependent antibody action (sperm immobilization, cytotoxicity). Experiments include isolation and characterization of immobilizaton antigens, iso- and autoantigenicity, examintion for necessary immunoglobulin (IgG, IgM) and complement components in the female tract and antifertility vaccine action of purified antigen. 3) To include the human condition sera from vasectomized men and "immunologically infertile" women are examined for auto- and isoantibodies to immunologically important human sperm antigen counterparts to those defined in (1) and (2) above. 4) Marine invertebrate gametes (e.g. sea urchins) are used in pilot studies to develop conceptual and technical possibilities when appropriate.